Israeli Prime Minister Benjamin Netanyahu has said his country is “at war” with Hamas militants in the Gaza Strip. Netanyahu's comments in a televised address mark his first since Hamas launched a major, multi-front attack on Israel at daybreak on Saturday. He ordered a call-up of reservists and promised that Hamas would “pay a price that it hasn't known until now.” “We are at war,” Netanyahu said. “Not an ‘operation,' not a ‘round,' but at war.” The prime minister also ordered the military to clear the infiltrated towns of Hamas militants that remained locked in gunfights with Israeli soldiers. Twenty-two people have been shot dead in Israel since the start of the offensive launched Saturday morning by Hamas, Israeli emergency services said in a statement early this afternoon. The press release from Magen David Adom, the Israeli equivalent of the Red Cross, also reports “hundreds of injured people”. Magen David Adom previously announced that a sixty-year-old woman had been killed by rocket fire. Hamas fired hundreds of rockets at Israel from the Gaza Strip on Saturday and infiltrated fighters into Israeli territory. It comes as Hezbollah congratulates Hamas for its “heroic operation” against Israel. Hailing from Lebanon, pro-Iranian Hezbollah, which boasts a powerful armed wing, congratulated the Islamist movement Hamas after the launch of a military offensive against Israel. Hezbollah, Israel's bete noire, maintains good relations with Hamas, which has controlled the Gaza Strip since 2007. Israel also struck several Hamas facilities in the Gaza Strip as part of Operation Iron Swords. "Dozens of Israeli fighter jets are currently attacking several targets belonging to the Hamas terrorist organisation in the Gaza Strip," the army said. On Saturday morning. Palestinian militants carried out an unprecedented infiltration into southern Israel, sending fighters across the border and firing thousands of rockets into the country. The rocket fire from several locations in the Palestinian territory began before 6:30 am local time and continued into the early morning. The Israeli army sounded sirens in the south and centre of the country, urging the population to stay close to shelters. The armed wing of Hamas, which has controlled the Gaza Strip since 2007, announced that it had launched "Operation Al-Aqsa Flood" against Israel and fired more than 5,000 rockets. Salah Arouri, an exiled Hamas leader, said the operation was a response “to the crimes of the occupation.” He said fighters were defending the Al-Aqsa Mosque in Jerusalem and the thousands of Palestinian prisoners held by Israel. Following a security cabinet meeting at the Israeli military headquarters in Tel Aviv, Defense Minister Yoav Gallant warned that Hamas “made a grave mistake” in launching barrages of rockets into southern and central Israel.  “The state of Israel will win this war,” Gallant said. One killed and more than a dozen injured A woman in her sixties was killed and 15 other people were injured in southern Israel, announced the Magen David Adom, the Israeli equivalent of the Red Cross. Twice in the morning, sirens sounded as far away as Jerusalem. Several explosions were heard around 9:00 am local time. One rocket fell on the town of Yavne, south of Tel Aviv, where a man was slightly injured by shrapnel, according to Magen David Adom.  Israel's army has closed roads in the area bordering the Gaza Strop.  In May, Israel launched an offensive against Palestinian Islamic Jihad in the Gaza Strip, triggering a five-day war between the Israeli army, Islamic Jihad and other armed groups in the territory that claimed the lives of 34 Palestinians and one Israeli woman. The launches came after weeks of heightened tensions along Israel's volatile border with Gaza, and heavy fighting in the Israeli-occupied West Bank. Hamas, which took power in Gaza in 2007, remained aloof from the conflict. Israel has imposed a strict blockade on the Gaza Strip since Hamas took control. Israel and Hamas have fought four wars since then. Israel has also built a massive fence along the Gaza border meant to prevent infiltrations. It goes deep underground and is equipped with cameras, high-tech sensors and sensitive listening technology. Since the beginning of the year, violence linked to the Israeli-Palestinian conflict has escalated, claiming the lives of at least 247 Palestinians, 33 Israelis, one Ukrainian and one Italian.